Olefinic slip-coating for automotive weatherseals

ABSTRACT

A weatherseal or belt-line seal for a vehicle is formed by extrusion of an olefin-based thermoplastic elastomer or vulcanizate (first TPV) as an elongate body of arbitrary length and cross-section. The cross-section is adapted for use in a particular location in the opening of a structure to be protected against wind and rain, for example around the glass of a window in a vehicle&#39;s door, or around the opening (at the periphery) in which the door is closed, so as to present at least one sealing surface against which the glass or door may be abutted to provide a seal against the elements. A slip-coating is co-extruded onto one or more longitudinal sealing surfaces of the body; the slip-coating contains a novel compatibilizer which allows thermoplastic polyurethane (TPU) to be chemically bonded to a graft copolymer of polypropylene (PP) and a compound having two anhydride groups. The reaction product of the grafted PP and the TPU effects a thermal bond with the sealing surface of the body. The slip-coating has a combination of softness and abrasion resistance which are uniquely suited for the purpose of the weatherseal.

FIELD OF THE INVENTION

This invention relates to a weatherseal for an opening in a structurethe interior of which is to be protected against wind and rain. Theweatherseal preferably having a relatively soft extrudate body, aportion of which is coated with a slip-coating of relatively harderelastomer, is formed as an extrudate of relatively hard elastomerthermally bonded as a slip-coating and forming an integral portion of asofter polymer. The slip-coating not only exhibits low frictionalcharacteristics and high abrasion resistance but also remarkablesoftness compared to that of conventional slip-coatings.

The Problem

Though available elastomers of extrudable thermoplastic vulcanizates(TPVs) are commonly used to produce weatherseals, the ever-increasingdemands of the marketplace seeks weatherseals with improved properties.Properties which are currently accepted but seek improvement are foundin TPV weatherseals having an elongate body or base portion which havebeen co-extruded with slip-coatings having a hardness of at least 50Shore D, Taber abrasion resistance measured at 500 cycles of at least50, and a coefficient of friction greater than about 0.3. Though it isknown that any one of the foregoing properties can be lowered, it is notknown how to lower all three properties and still produce a marketableweatherseal.

The goal is to produce a slip-coating which provides an exceptionallygood seal against entry of wind, snow and rain because of a criticalcombination of three specific properties, namely softness, good abrasionresistance, and low coefficients of friction; and to formulate theslip-coating containing a TPV which allows it to be thermally bonded tothe body so as to become an integral part of it, and to be pigmented orpainted with colors of choice.

BACKGROUND OF THE INVENTION

The term “elastomer” is used in the broad sense, in that the cured blendis extrudable as a dense solid TPV essentially free of macroscopicvoids, or a dense foam having a density in the range greater than about80% of that of the dense solid, and the TPV is re-processable, unlike athermoset resin. By “extrudable” is meant that a vulcanized blend can beprocessed in an available, commercial extruder or injection moldingmachine which provides internal mixing at a temperature in the rangefrom about 180° C. to 240° C. with a residence time less than 5 min,preferably in the range from 30 sec to 2 min. In such TPVs, which are“self-cured” and not physical blends, their combination of desirableelastic and thermoplastic properties depends on the respective amountsof “hard” and “soft” phases provided by each component, and theproperties of each component. The polyolefin phase is the continuous“hard” phase in which the rubber “soft” phase is present as discreteparticles. By varying the ratios of the components, one may providedesired hardness/softness, oil and temperature resistance, oxidationresistance, and extrudability, inter alia.

Commonly used weatherseals are provided with a flock or fibrous napagainst which the glass of an automobile's window abuts; thougheffective, the nap suffers from repeated use, either being abraded awayor being worn off. Moreover the process for depositing the nap iscomplicated and expensive.

The term “weatherseal” refers to an extrudate of elastomer intended foruse in any application where metal or glass parts are used with theextrudate in abutting contact therebetween, typically in the window of avehicle, or for a belt-line seal for a door. Weatherseals are known tobe co-extruded, being formed with a base portion made of a hard polymer,and a support portion made of a soft polymer, either or both of whichare coated with a coating which is a blend of two resins havingdifferent melting points (see U.S. Pat. No. 5,343,655 to Miyakawa etal). The term “co-extruded” is used herein to describe the substantiallyconcurrent extrusion of a body or support portion from one barrel andthe extrusion of an elastomer slip-coating from a second barrel, theslip-coating to be integrally bonded to the body or support portion. Thecoating may also be provided as a batten surface layer comprising nylon,polyurethane, fluoro-resin, polystyrene or polyolefin containingparticles of mica, molybdenum and/or graphite to form a rough surfacewith projections and recesses (see U.S. Pat. No. 5,441,685). For examplea filler of molybdenum disulfide particles provides a tape of afluorocarbon polymer with lubricity. Adhesively securing a tape of oneof the foregoing polymers (as the batten surface) to a base weathersealrequires coating the base with an adhesive, and additional steps; andsecuring the tape to curved or complex surfaces is difficult. Anothercoating provided as a batten surface layer has been co-extruded with aguide edging member using small and large particles of nylon 11 and/or12, or a polyolefin mixed with small and large particles of nylons 6and/or 66 or a fluorocarbon resin, having high melting points (see U.S.Pat. No. 5,447,671).

Still another weatherseal is provided by co-extruding a base polyolefinelastomer to form a support body which is coated with a co-extrudedprotective film of a mixture consisting of a polyolefin-based resinhaving low viscosity and high fluidity, and grains of particles of anadditive material which is a polyolefin-based resin having highviscosity and low fluidity (see U.S. Pat. No. 5,424,019). Morespecifically, the base material for the protective film is polyethylene(PE) having a melt flow rate greater than 0.6 g/10 min (ASTM D 1238 190°C.) and the additive material is in the form of grains and particles ofa high viscosity PE having a melt flow rate less than 0.1 g/10 min.

The co-extrusion and thermal bonding of a slip-coating to a body or baseportion of a weatherseal is conventional and essentially the same orsimilar equipment as used in the '019 patent is used in the process ofthis invention. A protective layer may also be provided with a layer ofcrystalline polyolefin and a rubber, and a layer of an ultrahighmolecular weight polyolefin which contacts the glass (see EP 0 860 314A1).

Still another slip-coating is provided with a TPV of chosen hardness,typically 50 Shore D, blending it with a thermoplastic polyolefin resinand doctoring the blend with various plasticizers, and fillers such asfatty acid amides and organopolysiloxanes to get the desired lowcoefficient of friction, also referred to as lubricity. (see JapanesePatent Application No. 7-346094 and JP 9176408A). The effect of theaddition of a semicrystalline polyolefin in combination with aplasticizer and a filler to a TPV is improved abrasion resistance andlubricity (low coefficients of friction). There is no suggestion thatinclusion of a thermoplastic polyurethane (TPU), normally incompatiblewith such a TPV, may provide any benefit, particularly when the TPVincludes a minor proportion by weight of a semicrystalline polyolefincopolymer. However, not only does the melt-blend of a TPV with acompatibilized TPU exhibit excellent abrasion resistance and lubricity,but it also has the ability to be integrally bonded to a TPV. Moreover,the novel TPV containing the compatibilized TPU can be colored either byinclusion of a pigment of choice, or by being painted with appropriatecommercially available paints, particularly urethane-based paints. Whenthe olefin copolymer is omitted from the melt-blend the slip-coating hasunacceptable Taber abrasion.

None of the prior art weatherseals provides an elongate body with acoextruded glass-abutting layer which is softer than 50 Shore D but hasa Taber abrasion which indicates abrasion damage low enough to indicatethat the slip-coating is neither worn away, or torn off. In addition,prior art weatherseals formed with a co-extruded slip-coatingdeliberately formulated to have a hardness lower than 50 Shore D arefound to have unacceptably poor Taber abrasion (measured by ASTM D1044-94), or poor friction characteristics which cause “sticking” of theglass to the weatherseal, particularly on hot days when the glass isexposed to bright sun. If formulated to have a hardness higher than 50Shore D, the weatherseal tends to leak in locations where the glass doesnot press against the sealing surface either sufficiently evenly, orfirmly. Moreover weatherseals harder than 50 Shore D lack “good hand”and fail to be squeak-free on either a hot day or a cold day. No priorart glass-abutting surface has the critical combination of softness,good abrasion resistance and lower coefficients of friction, provided bythe weatherseal of this invention.

It is known that PP may be modified by grafting an unsaturated monomerbearing an acid anhydride group to the PP, and reacting the graft(referred to as “mPP”) so formed with an a polymer having at least twogroups which are reactive to the anhydride group (see U.S. Pat. No.4,735,992) but there is no suggestion that the reaction product of a mPPand a thermoplastic polyurethane may be incorporated in a melt-blend ofa TPV to provide a slip-coating which is uniquely adapted for use on aweatherseal.

SUMMARY OF THE INVENTION

It has been discovered that the base of a weatherseal formed from a“first TPV”, may have thermally bonded to it a slip-coating of acopolymer layer containing thermoplastic polyurethane (TPU); theslip-coating is formed by melt-blending a “second TPV” with a reactionproduct of (i) a graft copolymer of polypropylene (PP), (ii) athermoplastic polyurethane (TPU) and (iii) a random copolymer of two ormore α-olefins having from 2 to about 12 carbon atoms; the graftcopolymer functions as a compatibilizer allowing TPU which is normallyincompatible with an olefin-based TPV to be molecularly connected in theslip-coating. The combination of specific properties of the slip-coatingis as follows: hardness lower than 50 Shore D, preferably in the rangefrom 85 Shore A to 45 Shore D; a Taber abrasion resistance (measured at500 cycles) in the range from about 15 to about 50; and coefficients offriction, both static and dynamic, in the range from about 0.1 to 0.4.This combination of properties provides smooth contact with, and releaseof a glass-abutting or door-abutting surface of the weatherseal;longevity in use; a paintable surface; excellent “freeze release”, thatis minimal sticking of the slip-coating to the surface of thewindow-glass or door; and no squeak when the window-glass is raised orlowered.

The foregoing combination of properties is found to be provided by aslip-coating comprising (i) an olefin-based thermoplastic elastomer(TPV) having a hardness in the range above 85 Shore A but below 50 ShoreD, (ii) a melt-blended reaction product of a graft copolymer of PP and aTPU which is otherwise incompatible with a TPV whether the rubber in theTPV is EPDM or butyl rubber, and (iii) from 5 to 30 parts of an α-olefincopolymer per 100 parts of slip-coating. The reaction product (referredto as mPP-g-TPU) is preferably formed by melt-blending and thermallycopolymerizing (i) a minor portion by weight of commercially availablepellets, or a powder, of a high molecular weight polypropylene (PP)modified by grafting a monomer bearing an anhydride group (mPP) with(ii) a major portion by weight of commercially available pellets of acompound having at least two groups which are reactive with theanhydride group, preferably thermoplastic polyurethane (TPU). ThemPP-g-TPU functions as a compatibilized TPU melt-blended with a secondTPV in the slip-coating, allowing it to be thermally bonded to a firstTPV extrudate of arbitrary length, and at the same time the mPP-g-TPUfunctions as a viscosity reducer which reduces the viscosity of themelt-blend (of second TPV with mPP-g-TPU). The ratio of second TPV tomPP-g-TPU is in the range from 20: 1 to 1: 20. The melt-blend of secondTPV and mPP-g-TPU has a viscosity lower than that of the first TPV whichis extruded in a cross-section suitable for its intended purpose in thewindow of a vehicle, or a belt-line seal for a door.

BRIEF DESCRIPTION OF THE DRAWING

The foregoing and additional objects and advantages of the inventionwill best be understood by reference to the following detaileddescription, accompanied with schematic illustrations of preferredembodiments of the invention, in which illustrations like referencenumerals refer to like elements, and in which:

FIG. 1 is a vertical cross-section illustrating a co-extrudedweatherseal such as is conventionally used in the upper portion of awindow provided in a vehicle's door and within which weatherseal theupper portion of the window's glass is sealingly held.

FIG. 2 is a vertical cross-section illustrating a co-extrudedweatherseal such as is conventionally used in the lower portion of awindow provided in a vehicle's door and within which weatherseal thelower portion of the window's glass is sealingly held when the glass iseither raised or lowered.

FIG. 3 is a vertical cross-section illustrating another co-extrudedweatherseal such as is conventionally used on either side of a windowprovided in a vehicle's door and in which weatherseal the side edges ofthe window's glass is sealingly held and reciprocated.

FIG. 4 is a schematic illustration of a slip-coating die in which anextrudate of a body of an extrudate from a first barrel of an extruderis coated with a slip-coating produced in a second barrel of anextruder.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In its most preferred embodiment the invention is a weatherseal coatedwith a slip-coating of a TPU-containing copolymer layer; in anotherembodiment, an article is made from the TPU-containing copolymer, suchas one requiring flexibility which withstands repeated elongation andwhich is subjected to abrasion. Such an article is an expansible bellowsused as a boot for a rack and pinion assembly, a boot for a constantvelocity joint, a dust cover for a shock absorber, and the like. Each issubject to abrasion due to friction generated when the expansiblebellows are squeezed together.

The Components

In the melt-blended olefin-based elastomer (whether first or second TPV)the preferred olefin is PP though it may include a minor proportion ofpolyethylene (PE), and the preferred rubber is selected from the groupconsisting of an ethylene-propylene-non-conjugated diene (EPDM) rubberand butyl rubber, the remainder being: processing oil or ester whichfunctions as a viscosity modifier, fillers, colorants, curing agent,antioxidants and other ingredients. Essential ingredients are thepolyolefin, the rubber and processing oil, the remainder being chosen tomeet the specific requirements for a particular intended use or purpose.The most preferred range of essential components based on the 100 partsby weight of the formulated TPV elastomer, are as follows: from about15% to 60% olefin; from about 10% to 35% EPDM rubber; and from about 15%to 45% processing oil. Such an olefin-based elastomer having a meltingpoint in the range from about 130° C. to 180° C. is present in a majoramount by weight in the body as well as the slip-coating of theweatherseal.

The first and second TPVs are most preferably chosen from elastomerscommercially available under the Santoprene® trademark. The hardness ofthe first TPV for the body of the weatherseal is preferably less than 60Shore D; the hardness of the second TPV for the slip-coating is lessthan 50 Shore D. The oil or ester is selected from synthetic hydrocarbonoils that are branched (for example, poly C₈-C₁₂ α-olefins); or, oilswhere the molecular structure is mostly hydrocarbon, but contains alimited amount of bound polar organic groups. Suitable oils in thisapplication do not exude from the weatherseal when exposed to a brightsun for an entire year.

The slip-coating is bonded to chosen surfaces of the body of theextrudate; in a specific example the slip-coating comprises amelt-blended TPV in combination with the mPP-g-TPU in which mPP is mostpreferably, maleated polypropylene. The α-olefin copolymer is present ina minor proportion by weight relative to the TPV, preferably less than30 parts per 100 parts of TPU-containing copolymer, so that it (theTPU-containing copolymer) most preferably has a hardness in the rangefrom about 30 Shore D to 45 Shore D.

The Body of the Weatherseal

The body of the weatherseal is provided by a commercially available,extrudable first TPV the composition of which is not narrowly criticalbut is preferably formed from the components described below. Theextrudate body may have a wide range of hardness from about 35 Shore Ato 80 Shore D, depending upon the particular application, but for use asa belt-line seal, or in a channel for the glass of a window, the body isrelatively soft, preferably in the range from about 50 Shore A to 35Shore D. The cross-section of the body is adapted to be held in or on aparticular portion of an opening which is to be sealed against theweather.

The Slip-Coating of TPU-containing copolymer

The slip-coating is provided by an elastomer layer of a second TPV whichis melt-blended with mPP-g-TPU; the second TPV may be the same as ordifferent from the first TPV used for the body. The compatibilized TPUmakes it possible to chemically integrate a large amount of TPU with thefirst and second TPVs. The PP may be grafted with any cyclic acidanhydride group such as maleic, citraconic, 2-methylmaleic,2-chloromaleic, 2-methoxycarbonylmaleic, 2,3-dimethoxycarbonylmaleic,and the like. In its most preferred embodiment a maleated PP (that is,PP grafted with maleic anhydride) compatibilizer is melt-blended with aTPU having a molecular weight in the range from 5,000 to 100,000. TheTPU is present in the range from about 40 to 99 parts by weight, morepreferably in the range from above 50 to about 95 parts TPU per 100parts of compatibilizer, the remainder being mPP; and the maleicanhydride in the mPP is present in the range from 0.1 to 2%, morepreferably in the range from 0.3 to about 1.5%. The mPP has a melt flowindex in the range from 10 to 1000.

The a-olefin copolymer is formed with a minor proportion of ethylene,and one or more higher olefins which are together present in a majoramount; higher olefins include propylene, 1-butene, 1-pentene, 1-hexene,2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene,5-methyl-1-hexene, 1-octene and 1-nonene. Homopolymers of an α-olefinare too crystalline and produce a slip-coating composition which hasexcellent lubricity but a hardness greater than 50 Shore D. Mostpreferred are commercially available copolymers of ethylene and a higherα-olefin in which the higher olefin is present in the range from 70 to99%, preferably 80 to 98%, as exemplified by propylene-ethylenecopolymers (PP-co-PE) and ethylene-octene copolymers (PE-co-PO).

In addition to the essential components identified above in theslip-coating composition, the TPU-containing copolymer may include anadditive selected from the group consisting of a plasticizer, filler andlubricant, any one of which may be present in no more than 10 parts byweight per 100 parts of TPU-containing copolymer. Suitable plasticizersare conventional paraffinic, naphthenic and aromatic processing oils.

Suitable fillers include calcium silicate, clay, kaolin, talc, silica,diatomaceous earth, powdered mica, barium sulfate, aluminum sulfate,calcium sulfate, basic magnesium carbonate, glass fibers, and carbonfibers, provided the filler is used in an amount small enough not toadversely affect either the hardness or the coefficients of friction ofthe TPU-containing copolymer.

Preferred silicas which may be used are micronized silica, fumed silica,a dry process white carbon referred to as “white carbon”, a wet-processwhite carbon, and synthetic silicate-type white carbon. Silica increasesthe Taber abrasion of the elastomer but improves its sliding and wearproperties, that is, lowers coefficients of friction. Preferably thesilica or any other filler is used in an amount small enough not toadversely affect either the hardness or the coefficients of friction, nomore than 10 parts, preferably 0.5 to 5 to parts per 100 parts ofTPU-containing copolymer.

Suitable inorganic lubricants are molybdenum disulfide and graphite;organic lubricants include higher fatty acids such as stearamide,oxystearamide, oleylamide, erucylamide, laurylamide, palmitylamide, andbehenic amide; methylol amides; amide types of higher fatty acids suchas methylene-bis-stearamide, ethylene-bis-stearamide,ethylene-bis-oleamide, and ethylene-bis-laurylamide; composite-typeamides such as stearyloleylamide, n-stearylerucylamide andN-oleylpalmitylamide; and special fatty amides commercially availableunder the trade name “Plastrodine” and “Plastrodine S” (FujisawaPharmaceutical Co., Ltd.). Preferably lubricant is used in an amountsmall enough not to adversely affect either the hardness or thecoefficients of friction, no more than 10 parts, preferably 0.5 to 5parts per 100 parts of TPU-containing copolymer.

Useful organopolysiloxanes are dimethyl polysiloxane, methylphenylpolysiloxane, methylhydrogen polysiloxane and modified polysiloxanessuch as epoxy-modified, alkyl-modified, amino-modified,carboxyl-modified, alcohol-modified, fluorine-modified, alkylarylkylpolyether-modified, epoxy polyether-modified, and polyether-modifiedpolysiloxanes. Preferably the organosiloxane is used in an amount smallenough not to adversely affect either the hardness or the coefficientsof friction, no more than 10 parts, preferably 2 to 8 parts per 100parts of TPU-containing copolymer.

The Process

The process for making a weatherseal comprises, (i) melt-blending afirst TPV in a first barrel to form a first TPV melt (ii) extruding thefirst TPV melt under suitable extrusion conditions through a firstextrusion die of predetermined cross-section to form the body of theweatherseal; (iii) melt-blending a second TPV, the same as or differentfrom the first, in a second barrel to form a second TPV melt (iv)extruding the second TPV melt under suitable extrusion conditionsthrough a second extrusion die of predetermined cross-section to form aslip-coating (v) contacting the body portion with the slip-coating (vi)and recovering a weatherseal having its body integrally bonded to theslip-coating, the weatherseal having the desired cross-section and theslip-coating presenting the desired surface-abutting surface.

The Weatherseal

Referring to FIG. 1 there is illustrated a weatherseal referred togenerally by reference numeral 10, formed by extruding a first TPV so asto have a body 11 which is snugly fitted into the upper portion 12 ofthe frame of a vehicle's window. The cross-section of such a weathersealwill vary depending upon the channel in which it is to be held, but ingeneral the cross-section is channel-shaped, and whether only sides ofthe channel are coated, or the bottom of the body is also coated,depends on whether the weatherstrip is to be used in the sides of thewindow, or in its upper portion. In FIG. 1, where it is used in theU-shaped channel 14 in the upper portion 12 of a window, a bumperportion 13 of the body 11 is preferably snugly held so as to have theupper edge of window glass 20 bump against the lower surface of thebumper portion. The weatherseal may also be attached with suitablefastening means (not shown) or with adhesive. The sides 15 and 16 of thebody extend downward on either side of the upper edge of the glass 20 inits raised position. The lower ends 17, 18 of each side are shaped sothat their outer surfaces (relative to the central vertical axis) aresnugly fitted against the inner surfaces of the channel 14. The innerportions of the lower ends 17, 18 of each side 15 and 16 respectively,are shaped so as to present vertical stubs 19 and 19′ which matinglysecure the glass 20 therebetween.

The inner opposed surfaces of each stub 19, 19′ has a slip-coating 21,21′ co-extruded thereon so that when the glass 20 is raised, asindicated by the arrow, it slides in contact between opposed slip-coatedinner surfaces of the stubs 19, 19′. During the co-extrusion, it isconvenient to allow the slip-coating 21, 21′ to be co-extruded on theouter downward facing surfaces of each lower end as well. A slip-coating22 is co-extruded onto the lower inner surface of the bumper portion 13so as to allow the glass 20 to be seated against 22. It will now beevident that raising and lowering the glass causes abrasion damage onthe opposed surfaces of the lower ends, and that a high coefficient offriction will cause the stubs 19 and 19′ to be pulled down when theglass is lowered, deforming or damaging them. A high coefficient offriction is not nearly as damaging when the glass is raised.

Referring to FIG. 2 there is illustrated a window glass 20 held betweenweatherseals 31, 32 which, in turn are securely held in the horizontallower walls 41, 42 of a door panel 40 of a vehicle. Each weatherseal, asinstalled in the door panel, is a substantially F-shaped mirror image ofthe other; each has vertical portions 33, 34 terminating in upperportions which include upper glass-abutting stubs 35, 36. Eachweatherseal also includes lower glass-abutting stubs 37, 38 below thestubs 35, 36 respectively. The lower surfaces of the upper stubs 35 and36 are provided with slip-coatings 45 and 46 respectively; and the lowersurfaces of the lower stubs 37 and 38 are provided with slip-coatings 47and 48 respectively. The door panel 40 is preferably fitted with acomplementary weatherseal 50 which is fitted around the walls 42, 43 ofthe outer door panel; and a lower portion 36′ of the upperglass-abutting stub 36 snugly overlies the complementary weatherseal 50,anchoring the weatherseal 32. To anchor the weatherseal 31, a lowerportion 35′ of upper glass-abutting portion 35 snugly overlies innerwall 44 of the door panel 40.

Another embodiment of an upper weatherseal used around an access-openingis illustrated in FIG. 3 in which the weatherseal 60 seals the peripheryof a glass window 70 which does not run in channels. Illustrated is theupper portion of a structure 80 in which a generally U-shaped channel 82depends from a panel portion 81. The channel 82 is shaped to have across-section corresponding to that of weatherseal 60 the base 61 ofwhich is snugly secured around its base and sides in the channel 82. Thelower surface of the lower portion 62 is coated with a slip-coating 65and the body is provided with longitudinal through-passages 63, 64 toallow the body 60 to be compressed by the upper edge of the glass window70.

As stated above, the co-extrusion of the slip-coating 21, 21′ and 22onto weatherseal 10 is effected in a conventional split blockslip-coating die 90 comprising die blocks 93 and 94 illustrated in FIG.4. Die block 93 is provided at a first surface with an entry port forthe body 11 of extrudate from barrel B1 of an extruder and, at a secondsurface displaced 90° from the first, with an entry port for aslip-coating from barrel B2 of an extruder. Die block 94 is providedwith slots 95 to deposit the desired width and thickness ofslip-coatings 21, 21′ and 22 on chosen longitudinal surfaces of theweatherseal 10; and die block 94 has an axial extrusion port 96 shapedto conform to the desired dimensions of the U-shaped weatherseal.

In the following illustrative examples, all references to “parts” are to“parts by weight”. All slip-coatings were produced in a 2″ diameterstaged, single step twin-screw extruder in which three zones in thebarrel were maintained at temperatures in the range from 160° C. to 200°C. in the first zone, 170° C. to 200° C. in the second zone, and 180° to200° C. in the third zone. The time during which the TPV stayed in thebarrel range from about 2 min to 8 min.

Abrasion resistance is measured by the Standard Test for Resistance ofTransparent Plastics to Surface Abrasion, ASTM D 1044-94, limited to 500cycles. Abrasion damage is judged by that percentage of transmittedlight which, in passing through the abraded track, deviates from theincident beam by forward scattering; only light flux deviating more than0.044 rad (2.5° ) on the average is considered in this assessment ofabrasive damage.

Static and dynamic coefficients of friction are measured by the StandardTest Method for Static and Kinetic Coefficients of Friction of PlasticFilm and Sheeting, designated ASTM D 1894-90. This test method coversdetermination of the coefficients of starting and sliding friction ofplastic film and sheeting when sliding over itself or other substancesat specified test conditions. The procedure permits the use of astationary sled with a moving plane, or a moving sled with a stationaryplane. Since both procedures yield the same coefficients of frictionvalues for a given sample, the latter is used.

In the following Table 1 three prior art slip-coatings are prepared bymelt-blending commercially available TPVs with a commercially availablerandom copolymer of predominantly PP and a minor proportion of PE. Aslip-coating is obtained by doctoring the blend with a silica filler,fatty acid amide and a silicone to lower its coefficients of frictionand provide reasonable resistance to abrasion damage.

TABLE 1 Slip-coating No. 1 2 3 Santoprene ® 123-50 80 — — Santoprene ®101-87 — 72 80 Escorene PD9012 20 20 20 Hisil 233  4  4 Kemamide E  4  2  0.5 Silicone MB50-001 —  6  6 Properties UTS, psi 2090 2620 2730 %Elongation 215 570 610 M100%, psi 2100 1300 1270 Hardness, Shore D 54D43D 42D Static COF 0.3 0.48 0.39 Kinetic COF 0.26 0.43 0.35 TaberAbrasion 77 50 40 (@ 500 cycles) Notes: 123-50 and 101-87 are 50 shore Dand 87 Shore A Santoprene elastomers which are dynamically vulcanizedalloys of polypropylene and EPDM Hisil 233 is silica Kemamide E isErucylamide from Witco Corporation Silicone MB 50-001 is a siliconemasterbatch from DowCorning.

It is evident that using a hardness of 50 Shore D (Santoprene 123-50) tolower coefficients of friction results in poor Taber abrasion resistance(the higher the number the greater the damage due to abrasion). Using asofter TPV Santoprene 101-87 (87 Shore A) and addition of the siliconedoes improve both % elongation and abrasion resistance but at theexpense of increasing friction even when the Hisil 233 is retained.

In the following formulations of slip-coating the 87 Shore A TPV isretained to maintain the desirable low hardness, and softness is furthercontributed by a relatively large proportion of the mPP-g-TPU whilemaintaining the same proportion of random copolymer PP-co-PE.

TABLE 2 4 Slip-coating No. Control 5 6 7 Santoprene ® 101-87 72 5 5 36Escorene ® PD9012 20 15 20 mPP-g-TPU 87 72 36 Kemamide ® E 2 2 2 2Hisil ® 233 Silicone MB50-001 6 6 6 6 Properties Hardness, Shore D 43 4044 41 Static COF 0.48 0.35 0.15 0.16 Kinetic COF 0.43 0.42 0.17 0.17Taber Abrasion 50 56 21 39 (@ 500 cycles) Notes: PP-g-TPU was preparedby melt mixing maleated PP (Polybond ® 3000 from Uniroyal) andThermoplastic urethane, Texin DP7 from Bayer Samples were prepared onBrabender plasticorder and compression molded.

It is evident that using a hardness of 87 Shore A to improve softnessand lower coefficients of friction results in excellent Taber abrasionresistance and the Hisil 233 is unnecessary. Though the same amount ofsilicone is added in each case, the abrasion resistance is best and COFslowest when the mPP-g-TPU is combined with the random copolymer of PPand PE.

In three of the following formulations of slip-coating the EPDM rubberin the prior art cintrol Santoprene 101-87 was replaced by a Trefsin®TPV in which PP is melt-blended with butyl rubber. In slip-coating #9,mPP-g-TPU is substituted for one-half of the Santoprene in the control;the same amount of mPP-g-TPU is used in formulations 10-12, theremaining one-half being Trefsin butyl rubber elastomer. The controlcontains no Trefsin or mPP-g-TPU. As before the random copolymer of PPand PE is retained and except for the control, all slip-coatings containthe same amount of mPP-g-TPU.

TABLE 3 8 Slip-coating No. Control 9 10 11 12 Santoprene 101-87 72 36 —— — Ampacet 49974 black — — 5 5 5 Trefsin W305 — — 31 — — Trefsin W306 —— — 3 — Trefsin W309 — — — — 31 Escorene PD9012 20 20 20 20 20 PP-g-TPU36 36 36 36 Kemamide E 2 2 2 2 2 Hisil 233 — — — — — Silicone MB5001 6 66 6 6 Properties Hardness, Shore D 43 40 36 39 37 Static COF 0.48 0.180.27 0.3 0.31 Kinetic COF 0.43 0.19 0.33 0.32 0.42 Taber @ 500 cycles 5036 43 58 54 Note to Table 3: PP-g-TPU was prepared by melt mixingmaleated PP (Polybond 3000 from Uniroyal) and Texin DP7 thermoplasticurethane from Bayer Samples were prepared on a Brabender Plasticorderand compression molded.

What is claimed is:
 1. A weatherseal for an opening in a structure theinterior or which is to be protected against wind and rain, comprising,an extrudate body comprising a first olefin-based thermoplasticvulcanizate or elastomer (first TPV) having a hardness in the range fromabout 35 Shore A to 80 Shore D; a slip-coating of a copolymer layerintegral with said body, thermally bonded to chosen glass-abutting ordoor-abutting surfaces thereof, said slip-coating comprising (i) asecond olefin-based thermoplastic vulcanizate or elastomer (TPV), thesame or different from said first TPV, (ii) a reaction product of (a) amelt-blended copolymer of an unsaturated monomer bearing an acidanhydride group grafted to polypropylene, with (b) a thermoplasticpolyurethane (TPU); and, (iii) a random copolymer of two or morea-olefins having from 2 to about 12 carbon atoms; said slip-coatinghaving a hardness lower than Shore D 50, a Taber abrasion resistance(measured at 500 cycles) lower than 50, and coefficients of friction,both static and dynamic, lower than about 0.4.
 2. The weatherseal ofclaim 1 wherein said body of first TPV has a hardness in the range from35 Shore D to 60 Shore D; said slip-coating has a hardness in the rangefrom about 30 Shore D to about 45 Shore D; said random copolymer ispresent in an amount from 5 to 30 parts per 100 parts of saidslip-coating; and, said reaction product is formed by melt-blending agraft copolymer of maleated polypropylene with said TPU.
 3. Theweatherseal of claim 1 wherein said second TPV has a hardness in therange from about 85 Shore A to 45 Shore D and said copolymer is ofethylene and a higher α-olefin in which copolymer the ratio of thehigher olefin to polyethylene is in the range from about 70 to 99%. 4.The weatherseal of claim 1 wherein a melt-blend of said second TPV andmPP-g-TPU has a viscosity lower than that of said first TPV.
 5. Theweatherseal of claim 1 wherein said slip-coating includes an additiveselected from the group consisting of a plasticizer, a filler and alubricant, any one of which is present in an amount small enough not toadversely affect either the hardness or the coefficients of friction, nomore than 10 parts by weight per 100 parts of TPU-containing copolymer.6. The weatherseal of claim 5 wherein said higher olefin is propylene,said filler is silica, and said lubricant is a fatty amide, each presentin an amount in the range from about 0.5 to 5 parts per 100 parts ofTPU-containing copolymer.